OSIRIS-REX: ENGINEERING CHALLENGES OF SAMPLING AN … · Terminator Orbit Plane (Edge On) De-Orbit Burn Checkpoint Burn Matchpoint Burn Slew to Inertially Fixed Attitude Lidar Range

OSIRIS-REX OVERVIEW AT JHU ON 10/17/16

OSIRIS-REX: ENGINEERING CHALLENGES OF

SAMPLING AN ASTEROID

DAVID EVERETT

OCTOBER 17, 2016

PRESENTED AT JOHNS HOPKINS

UNIVERSITY, “NASA'S

ASTEROID SAMPLE RETURN

MISSION - MEET THE STARS...”

OSIRIS-REX OVERVIEW AT JHU ON 10/17/16

LAUNCH! SEPTEMBER 8, 2016

• Launch highlights: https://www.youtube.com/watch?v=AG1pE90ue5w&feature=youtu.be

• Launch Video: https://youtu.be/ULfQdFY9PQM

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OSIRIS-REX OVERVIEW AT JHU ON 10/17/16 2

FLIGHT SYSTEM FACTS

• 2104 kg (4639 lbs), half is fuel!

• 2 meters (6.6 feet) per side

• 1200 W

• 8.5 m2 (91 square feet) of solar

panels

• Lithium ion batteries

• 5 Instruments:

• Measurements in x-ray,

visible and infrared

• Laser measurements

• Touch-and-Go Sampler

• Sample Return Capsule

It’s based on other planetary missions

(MAVEN, Juno, MRO)

OSIRIS-REX OVERVIEW AT JHU ON 10/17/16

EXPLORATION OF THE UNKNOWN

• OSIRIS-REx must retrieve sample from an asteroid that has never been seen up close

• Design Reference Mission provides the step-by-step plan to build our knowledge

• Created and maintained by project systems engineering team

• Touches all aspects of the mission design

• Drives mission architecture and requirements

• Design Reference Asteroid documents what we do know about Bennu and how well we know it (uncertainties)

• Created and maintained by the science team

• Based on many observations (Arecibo, Herschel, HST, Magellan 6.5-m, SOAR 4-m, Spitzer, TNG 3.6-m, VATT 1.8-m, VLT 8.4-m, WHT 4.2-m and Kuiper 1.5-m) as well as analysis

• Peer-reviewed information

• Drives some aspects of environmental requirements document

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OSIRIS-REX OVERVIEW AT JHU ON 10/17/16

80 days of margin

mitigates pre-Recon risks

185 days of margin

mitigates pre-TAG risks

42 days of margin

mitigates an aborted TAG

OPERATIONS TIMELINE

OSIRIS-REX OVERVIEW AT JHU ON 10/17/16

Terminator Orbit Plane

(Edge On)De-

Orbit

Burn

Checkpoint

Burn

Matchpoint

Burn

Slew to

Inertially Fixed

Attitude

Lidar Range

Threshold

Crossing

Lidar

Range

CheckTo Sun

Rotation

DirectionTo

Earth

Timeline

3.6 hr 18 min2

min10 min 8 min

De-Orbit

BurnLidar Range

Threshold CrossingLidar

Range

Check

Checkpoint

Burn

Matchpoint

Burn

TAG

TAG

TAG OPERATIONS CONCEPT

OSIRIS-REX OVERVIEW AT JHU ON 10/17/16

GUIDED TAG APPROACH

• Orbit knowledge error and orbit departure maneuver execution error lead to large dispersion at Checkpoint

• Range threshold and pre-Checkpoint LIDAR measurements allow closed loop corrections to Checkpoint maneuver to achieve original Matchpointlocation

• Matchpoint corrected to original TAG approach trajectory

Without guidance With guidance

OSIRIS-REX OVERVIEW AT JHU ON 10/17/16

DESIGN REFERENCE ASTEROID

• Orbital Properties• Known extremely well, through ground-based astrometry and radar

observations in 1999, 2005, and 2011

• Approach imagery will be easy

• Bulk Properties• Size and shape known to within about 10 m

• Mass and density uncertainty is reasonable for navigation analysis

• Rotational Properties• Spin rate known to 0.05%

• Pole known to within 2 degrees

• Radar Properties• Does not drive mission design

• Photometric Properties• Drives camera design

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OSIRIS-REX OVERVIEW AT JHU ON 10/17/16

DESIGN REFERENCE ASTEROID (CONT.)

• Spectroscopic Properties

• Drives spectrometers

• Thermal Properties

• Thermal model used for spacecraft thermal analysis

• Thermal modeling done with engineering feedback to ensure

results were useful

• Engineering tools assume spherical object

• Surface Analog Properties

• Used for TAG simulations

• Environmental Properties

• Satellites (stability, size limit, etc.)

• Dust

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OSIRIS-REX OVERVIEW AT JHU ON 10/17/16

SRC FROM STOWCAM, ILLUMINATED BY STRAY LIGHT

OSIRIS-REX OVERVIEW AT JHU ON 10/17/16

SAMPLE RETURN CAPSULE NEARLY IDENTICAL TO

STARDUST SRC

• Stardust successfully returned a sample from a comet’s tail, but one of the parachute deployment pyros did not fire (the other one did)

• OSIRIS-REx performed some testing which discovered an unexpected shock environment, likely explaining the issue

• Other testing uncovered issues with the parachute cord

• Just because something works once doesn’t mean it will work reliably a second time.

• Reliability of spacecraft is outside the experience of every-day life.

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MASS GROWTH

OSIRIS-REX OVERVIEW AT JHU ON 10/17/16

THIS JOB IS DIFFICULT!

• Space missions are really hard because:• It requires a tremendous amount of energy to get into space—

essentially a controlled explosion

• Once on its way, it would take another launch to get to the spacecraft and fix any hardware problems

• The level of reliability is beyond everyday experience

• A single failure can end a mission

• We do these things in space, “not because they are easy, but because they are hard.” --JFK

• My job is fun because it is hard.

• A successful mission is the product of many people and many perspectives